1. Field of the Invention
The present invention relates to an apparatus for checking dimensions of mechanical parts, comprising a support base, first and second reference rests, for mechanically positioning first and second mechanical parts, measuring units coupled to the support base for checking both the first and the second parts and driving and control units adapted to cause a mutual displacement between the measuring units and the reference rests for achieving a mutual positioning between the measuring units and the first and second parts.
2. Description of the Prior Art
As it is known, the parts that are employed in the mechanical industry, for example in the motor car industry, normally are subjected to subsequent machining operations in the same or, more frequently, in different machine tools.
In particular, with reference to turning machines, although the modern lathes for mass production are very broadly automated and at the same time flexible, due to the use of computer numerical controls, automatic systems for part handling and tool replacement, rotary tools and also, recently, automatic systems for jaw changing, very frequently machining operations are performed, in which a first part is loaded into the chuck of a first lathe--that grips it at an end--is machined by this lathe, then is unloaded and loaded into the chuck or another lathe that grips it at the other end, in order to machine the part in correspondence with the portion previously gripped by the chuck of the first lathe. Of course, while the second lathe machines the first part, the first lathe machines a subsequent part, and so on.
It is also known to use--in view of the trend to reduce the tolerances of the machined parts, to automate the operations consequently diminishing the number of operators or eliminating them, and to shorten the cycle times--measuring apparatuses for automatically checking the dimensions of the machined parts. In particular, known apparatuses are adapted to "post-process" check parts machined in lathes as far as internal or external diameters, thicknesses, longitudinal distances, cylindricity, etc. are concerned.
Usually, these apparatuses are served by the same automatic workhandling systems that serve the lathe (pallet conveyors, robots, gantry loaders, etc).
Since the modern lathes are adapted to machine--depending upon relevant programs loaded into computer numerical controls--parts of different types with very short cycle times and in view of a rising trend towards batch machining, important features of the post-process measuring apparatuses are the flexibility, i.e. the capability of checking different parts without the need of complex operations for retooling of the apparatus, and the quickness, in addition--of course--to high accuracies and repeatabilities of the measurements.
The obtainment of a suitable compromise among these contrasting requirements is not easy and generally involves high costs for the measuring apparatuses. In order to reduce the costs of measuring apparatuses adapted to check parts of different types, it is known to use a common handling system capable of performing a mutual displacement between measuring means and a plurality of parts, positioned by mechanical reference means.
In particular, German Pat. No. 1101777 describes an apparatus in accordance with the preamble of the first claim, comprising a rotary disc--with mechanical reference means for positioning a plurality of parts, of different types, in correspondence with the periphery of the disc--and a plurality of stationary measuring stations. The parts are displaced to relevant measuring stations through step by step rotations of the disc.
This known apparatus is not flexible as far as the measuring means are concerned, because every station is adapted to check a determined type of part. Therefore, this apparatus does not meet the requirements necessary for the abovedescribed applications.